The processing of cellulosic material such as cotton fiber into a material ready for garment manufacture involves several steps: spinning of the fiber into a yarn; construction of woven or knit fabric from the yarn; and subsequent preparation, dyeing and finishing operations. The preparation process, which may involve desizing (for woven goods), scouring, and bleaching, produces a textile suitable for dyeing.
A. Scouring: The scouring process removes much of the non-cellulosic compounds naturally found in cotton. In addition to the natural non-cellulosic impurities, scouring can remove residual manufacturing introduced materials such as spinning, coning or slashing lubricants. Conventional scouring processes typically utilize highly alkaline chemical treatment, which results not only in removal of impurities but also in weakening of the underlying cellulose component of the fiber or fabric. Furthermore, chemical scouring creates environmental problems in effluent disposal, due to the chemicals employed and the materials extracted from the fibers. A superior method involves the use of enzymes, particularly pectinases, for scouring, as disclosed, e.g., in U.S. patent application Ser. No. 08/977,587, filed Nov. 25, 1997, now U.S. Pat. No. 5,912,407.
B. Dyeing: Dyeing of textiles is often considered to be the most important and expensive single step in the manufacturing of textile fabrics and garments. The major classes of dyes are azo (mono-, di-, tri-, etc.), carbonyl (anthraquinone and indigo derivatives), cyanine, di- and triphenylmethane and phthalocyanine. All these dyes contain chromophoric groups which give rise to color. There are three types of dyes involving an oxidation/reduction mechanism, i.e., vat, sulfur and azoic dyes. The purpose of the oxidation/reduction step in these dyeings are to change the dyestuff between an insoluble and a soluble form.
Processing and dyeing procedures are performed in either a batch or continuous mode, with the fabric being contacted by the liquid processing stream in open width or rope form. In continuous methods, a saturator is used to apply chemicals to the fabric, after which the fabric is heated in a chamber where the chemical reaction takes place. A washing section then prepares the fabric for the next processing step. Batch processing generally takes place in one processing bath whereby the fabric is circulated through the bath. After a reaction period, the chemicals are drained, fabric rinsed and the next chemical is applied. Discontinuous pad-batch processing involves a continuous application of processing chemical followed by a dwell period which, in the case of cold pad-batch, might be one or more days.
Regardless of whether batch, continuous, or discontinuous pad-batch methods are used, scouring and dyeing steps have not heretofore been compatible; consequently, it has been necessary to rinse or otherwise treat the fabric or to replace the treating solutions between scouring and dyeing. Thus, there is a need in the art for harmonization of scouring and dyeing methods so that they can be performed in a single bath, whether simultaneously or sequentially, so as to shorten processing time, conserve materials, and reduce the waste stream.